linux-ext4 - Re: [PATCH v3] e2fsck: do not read EA header beyond the end of an inode

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Message-ID: <20151128215444.GE10580@birch.djwong.org>
Date:	Sat, 28 Nov 2015 13:54:44 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	Artemiy Volkov <artemiyv@....org>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH v3] e2fsck: do not read EA header beyond the end of an
 inode

On Thu, Nov 26, 2015 at 08:59:54PM +0000, Artemiy Volkov wrote:
> In check_inode_extra_space(), if we attempt to read an EA header at
> the end of the extra space, in a corrupted filesystem it may result in
> a read beyond the bounds of the inode. Add a check to prevent this.
> 
> Reproduced by running ./test_one --valgrind f_write_ea_toobig_extra_isize.
> 
> Signed-off-by: Artemiy Volkov <artemiyv@....org>
> ---
> 
> A quick fix to v1 which wrongly uses spaces instead of tabs.
> Correct a nonexistent struct ext2_inode_large field name used in v2.
> 
>  e2fsck/pass1.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/e2fsck/pass1.c b/e2fsck/pass1.c
> index 0a8e23e..71ea943 100644
> --- a/e2fsck/pass1.c
> +++ b/e2fsck/pass1.c
> @@ -482,6 +482,10 @@ static void check_inode_extra_space(e2fsck_t ctx, struct problem_context *pctx)
>  		return;
>  	}
>  
> +	/* check if there is no place for an EA header */
> +	if (inode->i_extra_isize >= max - sizeof(__u32))
> +		return;
> +

Looks reasonable enough.
Acked-by: Darrick J. Wong <darrick.wong@...cle.com>

--D

>  	eamagic = (__u32 *) (((char *) inode) + EXT2_GOOD_OLD_INODE_SIZE +
>  			inode->i_extra_isize);
>  	if (*eamagic == EXT2_EXT_ATTR_MAGIC) {
> -- 
> 1.7.10.4
> 
> --
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